The present invention relates to an optical head of an optical disk memory, which is an apparatus for optically recording and reproducing information, and an optical head feed apparatus thereof.
In this so-called information age, many attempts are being actively made to develop new techniques for high-density large-capacity memories, which constitute the core of information technology. In addition to high density and large capacity, high reliability, rewritability and the like are required of memories, and among memories satisfying these requirements, optical disk memories, such as photomagnetic disks, are attracting particular note.
Many reports can be found on techniques pertaining to optical heads for use with optical disks. Out of various optical heads for use with optical disks, an optical head for use in minidisk apparatuses and the like, which is an optical head for rewritable photomagnetic disks, will be described below with reference to accompanying drawings.
FIG. 7 schematically illustrates an external view of a conventional optical head for use with minidisks and the like. A description of its configuration and operation will follow.
In FIG. 7, reference numeral 1 denotes an optical disk (not shown in the plan), and 2, a light receiving/emitting element configured as a single device mounted inside with a semiconductor laser chip, which is a light emitting section emitting a laser beam, as well as an optical signal detecting section for receiving reflected light resulting from the reflection of this laser beam by the optical disk 1 and detecting various signals.
Reference numeral 3 denotes a mirror for letting the laser beam from the light receiving/emitting element 2 reach the optical disk 1; 4, an objective lens (not shown in the plan) for focusing the laser beam reflected by the mirror 3 on the optical disk 1 and forming a minute light spot; and 5, an objective lens actuator (not shown in the plan) for letting the objective lens 4 follow any eccentricity or surface oscillation of the optical disk 1.
Reference numeral 6 denotes a magnetic head (not shown in the plan) for realizing, where the optical disk 1 is a recordable disk, so-called magnetic field-modulated recording by applying a modulated magnetic field; 6a, a fitting section for fixing the magnetic head 6 to a resin-made bench 7; 7, a resin-made bench on which these parts are mounted; 7a and 7b, reference sections into which shafts 8a and 8b are to be inserted, respectively; 7c, a light receiving/emitting element fixing section to which the light receiving/emitting element 2 is to be fixed; and 7d, a mirror fixing section to which the mirror 3 is to be fixed.
Reference numeral 9 denotes a flexible wiring board to be connected to an external circuit (not shown). To this board, the light receiving/emitting element 2 having a light emitting section and an optical signal detecting section for causing a semiconductor laser to emit light and detecting information signals from the optical disk 1 is electrically connected in a position 9a by soldering a wire or otherwise.
Further, the flexible wiring board 9 is mounted with a high-frequency superimposing circuit (not shown) for reducing noise due to returning light from the optical disk 1.
As described above, in the optical head composed of parts mounted on the resin-made bench 7, a laser beam is emitted by the light receiving/emitting element 2 as power is fed from the flexible wiring board 9, and the objective lens 4 forms a minute light spot in a prescribed position on the optical disk 1 as the objective lens actuator 5 is driven, similarly receiving power feed from the flexible wiring board 9 (the section for power feed to the actuator is not shown).
When a read-only optical disk 1 is to be read back, the magnetic head 6 does not operate, and the light receiving/emitting element 2 detects the so-called reflected light quantity of the optical disk 1. Where the optical disk 1 also permits recording, when it is recording, the light receiving/emitting element 2 emits optical power of a certain intensity, and performs so-called magnetic field-modulated recording with modulated signals from the, magnetic head 6. During a reproducing process, the magnetic head 6 does not operate, and the light receiving/emitting element 2 detects rotation of the polarizing surface from the optical disk 1 to implement the reproducing function.
Incidentally, although the above-described configuration can help reduce the cost and weight of the bench compared with a conventional die-cast metal bench by using a resin as its material, the resin-made bench, which is inferior in thermal conductivity to a metallic bench which excels in heat radiation, reduces head radiation by the semiconductor laser.
FIG. 8 shows the variation in the junction temperature of the semiconductor laser over time. (3) in FIG. 8 shows the temperature rise of the light receiving/emitting element by itself, and (2), its temperature rise when the light receiving/emitting element is mounted on a metallic bench. Comparison of the two curves reveals an approximately 1.9 times as great a rise when the light receiving/emitting element is by itself.
The condition of the light receiving/emitting element mounted on a resin-made bench can be regarded as substantially the same as that of the light receiving/emitting element by itself. However, where a resin-made bench is used, there is the problem that the temperature rise of the light emitting section shortens the service life of the semiconductor laser.
Moreover, when the temperature of the semiconductor laser rises, the amperage required to emit the same optical power also increases, entailing the problem of increased power consumption.
Furthermore, in a recording type optical head, the semiconductor laser is caused to emit light under high-frequency superimposition to reduce noise due to returning light.
However, a configuration of the optical head using a resin-made bench also involves the problem that the ground of the optical head consists only of a flexible wiring board connected to an external circuit, and can be provided with no firm grounding.
Another example of the disk recording/reproducing apparatus according to the prior art will be described below.
FIGS. 26, 27, 28, 29, 30 and 31 are schematic configurational diagrams of its optical head according to the prior art and diagrams for describing its operating principle.
FIG. 26 shows an exploded perspective view of the optical head. Reference numeral 109 denotes an integrated unit, part of which is illustrated in FIG. 30. Reference numeral 134 denotes a flexible circuit shown in FIG. 27. FIG. 28 illustrates a state in which the flexible circuit 134 is fitted to the integrated unit 109. FIG. 32(a) shows an exploded perspective view, and (b), an overall perspective view of the optical head.
Herein, reference numeral 101 denotes a silicon substrate; 102, a semiconductor laser fixed over the silicon substrate 101; 3, a multi-divided light detector formed by an IC process over the silicon substrate 101; 104, a radiator plate for holding the silicon substrate 101 in a thermally conductive state via silver paste; 105, a terminal wire-connected from the multi-divided light detector by wire bonding or the like; and 106, a resin package for holding the silicon substrate 101, the radiator plate 104 and the terminal 105.
FIG. 31 shows the optical configuration of the optical head. Reference numeral 107 denotes a hologram element (diffraction grating) formed of resin; and 108, a composite element composed of a beam splitter 108a, a folded mirror 108b and a polarizing-separating element 108c. 
What is integrally configured of the elements denoted by 101 through 108 above is defined to be the integrated unit 109.
Reference numeral 110 denotes a reflector mirror; 111, an objective lens fixed to an objective lens holder 112; 113, a photomagnetic recording medium having a magneto-optic effect; 114, an objective lens drive unit for driving the objective lens in the focusing and radial directions of the photomagnetic recording medium 113; and 115, a base constituting a component element of the objective lens drive unit 114. The objective lens drive unit consists of parts denoted by 111, 112 and 115.
Reference numeral 116 denotes a metallic optical bench; 117, a light spot, formed on the multi-divided light detector 103, for detecting a focusing error signal; 118, a light spot, formed on the multi-divided light detector 103, for detecting a tracking error signal; 119, a main beam (P polarized light) formed on the multi-divided light detector 103; 120, a main beam (S polarized light) formed on the multi-divided light detector 103; 121, a focusing error signal light receiving area; 122 and 123, tracking error signal light receiving areas; 124, an information signal light receiving area; 125, a subtractor; 126, an adder; 127 and 128, focuses of the focusing error signal detecting light spot; 130, a light spot formed on the photomagnetic recording medium 113; 131, an adhesive; 132, a radiator plate; 133, optical head cover; 134, a flexible circuit; and 129, a radiator hole for inserting a radiator plate 132 configured in the flexible circuit 134.
The reflector mirror 110 is fixed to the optical bench 116. The terminal 105 of the integrated unit 109 is fixed to the flexible circuit 134 by soldering (the part of the flexible circuit 134 in which a hole 129 is bored as shown in FIG. 27 is folded downward as shown in FIG. 28(a); the radiator plate 132 is fitted into a space S formed by that folding; and a plate spring part which the radiator plate 132 has penetrates the radiator hole 129 to come into contact with the radiator plate 104).
After that, it is inserted into the optical bench 116, and both ends of the radiator plate 132 are fixed to the optical bench 116 as illustrated in FIG. 10.
In this way, it is tacked by the application of a preload by the radiator plate 132 in the Z direction (the direction of the optical axis), and the fixing of the optical bench 116 and the resin package 106 by adhesion results in fitting and fixing of the integrated unit 109 into the optical bench 116.
As a result, the dimensions of the optical bench 116 are so determined that the light receiving surface of the multi-divided light detector 103 be positioned between the focuses 127 and 128 of the light spot in the Z direction (the direction of the optical axis).
On the other hand, the semiconductor laser 102 is fixed to the silicon substrate 101 in a thermally conductive state by soldering or otherwise and wire-connected onto the multi-divided light detector 103 by wire bonding.
The multi-divided light detector 103 is fixed to the radiator plate 104 in a thermally conductive state via silver paste, and heat generated by the semiconductor laser 102 is transmissive to the radiator plate 104 via the silicon substrate 101. The multi-divided light detector 103 and the terminal 105 are wire-connected by wire bonding, and the terminal 105 is soldered onto the solder part of the flexible circuit 134.
Heat accompanying the light generation of the semiconductor laser 102 is transmitted to the radiator plate 132, which is in contact with the radiator plate 104, and radiated by the metallic optical bench 116.
The operation of the example of the prior art configured as described above will be explained below.
Light emitted from the semiconductor laser 102 is reflected by an edged mirror (reflector mirror) formed over the multi-divided light detector 103 by etching or otherwise with its optical axis varied by 90 degrees. The light reflected by the edged mirror is separated into a plurality of different luminous fluxes by the hologram element 107.
The plurality of different luminous fluxes are transmitted by the beam splitter 108a of the composite element 108, reflected by the reflector mirror 110, and condensed by the objective lens 111 fixed to the objective lens holder 112 into the light spot 130 of about 1 micron in diameter on the photomagnetic recording medium 113.
A luminous flux reflected by the beam splitter 108a of the composite element 108 comes into incidence on a light receiving element for laser monitoring (not shown) to control the drive current for the semiconductor laser 102.
The light reflected from the photomagnetic recording medium 113 travels over a reverse route, is reflected and separated by the beam splitter 108a of the composite element 108, comes into incidence on the folded mirror 108b and the polarizing-separating element 108c, separated into mutually orthogonal luminous fluxes having two polarized light components, and comes into incidence on the information signal light receiving area 124.
Out of the reflected light from the photomagnetic recording medium, the luminous flux transmitted by the beam splitter 108a is separated into a plurality of different luminous fluxes by the hologram element 107, and condensed into the focusing error signal light receiving area 121 and the tracking error signal light receiving areas 122 and 123. Focus servo is accomplished by the so-called SSD method, and tracking servo, by the so-called push-pull method.
Further, by computing the difference between the main beam 119 consisting of the P polarized light and the main beam 120 consisting of the S polarized light, it is made possible to detect photomagnetic disk information signals by a differential detecting method. Further by adding them, detection of prepit signals is made possible.
In the optical head configured as described above, in order to obtain desired detection signals with the reflected light from the photomagnetic recording medium 12, the relative positions of the semiconductor laser 102, the objective lens 111 and the multi-divided light detector 103 are adjusted at the time of assembly. Referring to FIGS. 32(a) and (b), the adjustment of the focusing error signal and the tracking error signal is accomplished by shifting the objective lens drive unit 114 in the Y and x directions while holding the base 115 with an external jig (not shown) so as to adjust the outputs of the tracking error signal light receiving areas 122 and 123 to be substantially equal.
This adjustment eventually serves to align the center of the objective lens 111 with respect to the center of the light emitting axis of the semiconductor laser 102 as shown in FIG. 26.
On the other hand, the adjustment of the relative inclinations of the photomagnetic recording medium 113 and the objective lens 111 is accomplished by carrying out skew adjustment xcex8R in the radial direction (around the Y axis) and skew adjustment xcex8T in the tangential direction (around the X axis) while holding the base 115 with an external jig (not shown). After these adjustments, with the adjustment kept as it is, the base 115 is adhered and fixed to the optical bench 116 using the adhesive 131.
In the foregoing way, the focusing error signal and the tracking error signal are adjusted, and skews are adjusted, and four points are adhered and fixed to complete the optical head.
In the above-described configuration according to the prior art, however, as the radiator plate 132 is in contact with the radiator plate 104 by having its plate spring part penetrate the hole 129, it is difficult to achieve high-precision interplanar contact between the radiator plate 132 and the radiator plate 104.
As a consequence, even if the optical bench 116 is made of metal, the contact is only point to point or line to line, resulting in serious deterioration in heat transfer efficiency and heat radiation efficiency. The prior art therefore involves the problem that, where an even more powerful laser is used, heat radiation performance is insufficient if heat radiation uses only the optical bench 116 which enhances the heat transfer efficiency of the radiator plate 132 and the radiator plate 104.
Or where the optical bench 116 is made of resin, as the heat generated by the semiconductor laser 102 when it emits light is radiated only by the radiator plate 132 via the silicon substrate 101 and the radiator plate 104, both the heat transfer efficiency and the heat radiation efficiency are extremely poor, inviting a temperature rise in the semiconductor laser 102 itself, resulting in the problem that the drive current increases, the recording/reproduction time is seriously deteriorated by an increase in current consumption under drive by a battery, and it is made difficult to save the power consumption of the optical head.
The present invention is intended, in view of the above-described problems with the prior art, to provide an optical head capable of substantially enhancing heat radiation efficiency.
One aspect of the present invention is an optical head comprising:
a light source for emitting luminous energy recordable on a recording medium,
a heat radiating section, in contact with said light source, for radiating heat which accompanies the light emission thereof, and
a resin-made bench for mounting and fixing said elements.
This has an effect to enable the heat generated by the light source to escape from the heat radiating section in contact with the light source, to restrain the temperature rise of the light source, thereby extending the service life of the semiconductor laser and at the same time, through the lowering of the semiconductor laser temperature, to reduce the operating current and accordingly the power consumption.
Another aspect of the present invention is the optical head as described above, characterized in that said resin-made bench and said heat radiating section are formed by integral molding, and a part of said heat radiating section is exposed to space.
This enables the heat generated by the light source to escape from the heat radiating section in contact with the light source, to restrain the temperature rise of the light source, thereby extending the service life of the semiconductor laser and at the same time, through the lowering of the semiconductor laser temperature, to reduce the operating current and accordingly the power consumption. Also, its integrated formation has another effect to facilitate the packaging work.
Still another aspect of the present invention is the optical head as described above, characterized in that a threaded part is formed in said heat radiating section, one end of said heat radiating section is in contact with the back surface of said light source, tightening by said threaded part causes the end of said heat radiating section to support said light source, and
a part of said heat radiating section is exposed to space.
This has an energizing effect to fix the light receiving/emitting element from behind and at the same time a heat radiating effect.
Yet another aspect of the present invention is the optical head as described above, characterized in that one end of said heat radiating section is in contact with the back surface of said light source and the other end of same has a guide section which is in contact with a shaft supporting said optical head.
This enables the heat generated by the light source to escape from the heat radiating section to a shaft, further gives a heat radiating effect, thereby making it possible to extend the service life of the semiconductor laser and at the same time to reduce the operating current and accordingly the power consumption. Furthermore, the ground of the light source is dropped to the shaft through the heat radiating section to give firm grounding, thereby exerting an effect against unnecessary radiation.
Still yet another aspect of the present invention is the optical head as described above, characterized in that one end of said heat radiating section is in contact with the back surface of said light source and the other end of same has a spring section for suppressing a shaft supporting said optical head.
This makes it possible to eliminate the play of the resin-made bench and the shaft, resulting in an effect to ensure stable operation even in an environment where there is much vibration, such as when mounted on a vehicle.
A further aspect of the present invention is the optical head as described above, characterized in that one end of said heat radiating section is in contact with the back surface of said light source and the other end of same has an engaging section which engages with a threaded shaft for supporting and shifting said optical head.
As this results in combined use by the heat radiating section of a member engaging with the shaft, there is an effect to help reduce the number of parts.
A still further aspect of the present invention is an optical head comprising:
a light source for emitting luminous energy recordable on a recording medium,
a heat radiating section, in contact with said light source, for radiating heat which accompanies the light emission thereof,
a resin-made bench for mounting and fixing the aforementioned elements, and
a magnetic head mechanism for applying magnetic field-modulation signals, wherein
one of said heat radiating section is in contact with the back surface of light source and the other of same is in contact with a metallic member of said magnetic head mechanism.
This provides a head radiation effect by letting the heat escape from the heat radiating section to the magnetic head, thereby making it possible to extend the service life of the semiconductor laser and at the same time to reduce the operating current and accordingly the power consumption.
Another aspect of the present invention is an optical head comprising a light source for generating luminous energy required for recording on a disk-shaped information recording medium or reproducing information recorded on said disk-shaped information recording medium; a radiator plate, in contact with said light source either directly or indirectly, for guiding heat which accompanies the emission of light by said light source; an objective lens which is means for focusing light on said disk-shaped information recording medium; an objective lens drive unit for driving said objective lens in the focal and radial directions of said disk-shaped information recording medium; a light receiving element for receiving light reflected from said disk-shaped information recording medium; a sheet-shaped flexible circuit for feeding power to said light source and said light receiving element and communicating signals from said light receiving element; and an optical bench holding at least said light source, said objective lens drive unit, said radiator plate and said light receiving element, wherein:
said radiator plate is brought into contact with a heat transfer section provided in said flexible circuit and, by causing said flexible circuit to guide heat from said radiator plate, heat generated by said light source is radiated through said flexible circuit and said radiator plate.
Further, another aspect of the present invention is an optical head comprising a light source for generating luminous energy required for recording on a disk-shaped information recording medium or reproducing information recorded on said disk-shaped information recording medium; a radiator plate, in contact with said light source either directly or indirectly, for guiding heat which accompanies the emission of light by said light source; an objective lens which is means for focusing light on said disk-shaped information recording medium; an objective lens drive unit for driving said objective lens in the focal and radial direction of said disk-shaped information recording medium; a light receiving element for receiving light reflected from said disk-shaped information recording medium; a sheet-shaped flexible circuit for feeding power and communicating signals to said light source and said light receiving element; a thermally conductive heat transfer member; an optical bench for holding at least said light source, said objective lens drive unit, said radiator plate, said light receiving element and said heat transfer member; and a thermally conductive optical head cover fixed to said optical bench, wherein:
said radiator plate and said heat transfer member are brought into contact with each other, said heat transfer member is caused to guide heat from said radiator plate and, by bringing into contact said heat transfer member and said optical head cover with each other, heat generated by said light source is radiated by said light source through said optical head cover, said heat transfer member and said radiator plate.
Further, another aspect of the present invention is an optical head comprising a light source for generating luminous energy required for recording on a disk-shaped information recording medium or reproducing information recorded on said disk-shaped information recording medium; a heat radiating section, in contact with said light source, for guiding heat which accompanies the emission of light by said light source; an objective lens which is means for focusing light on said disk-shaped information recording medium; an objective lens drive unit for driving said objective lens in the focal and radial direction of said disk-shaped information recording medium; a light receiving element for receiving light reflected from said disk-shaped information recording medium; a sheet-shaped flexible circuit for feeding power to said light source and said light receiving element and communicating signals from said light receiving element; a thermally conductive heat transfer member; an optical bench for holding at least said light source, said objective lens drive unit, and said heat transfer member, said radiator plate and said light receiving element; and a thermally conductive optical head cover fixed to said optical bench, wherein:
said radiator plate is brought into contact with a heat transfer section provided in said flexible circuit to cause said flexible circuit to guide heat from said radiator plate; heat generated by said light source is radiated through said optical head cover, said flexible circuit and said radiator plate by bringing into contact said the heat transfer section of said flexible circuit and said optical head cover with each other; said radiator plate and said heat transfer member are brought into contact with each to cause said heat transfer member to guide heat from said radiator plate; and by bringing into contact said heat transfer member and said optical head cover with each other, heat generated by said light source is radiated through said optical head cover and said heat transfer member.
Further, another aspect of the present invention is an optical head feed apparatus for feeding an optical head, said optical head having a light source for generating luminous energy required for recording on a disk-shaped information recording medium or reproducing information recorded on said disk-shaped information recording medium; a radiator plate, in contact with said light source either directly or indirectly, for guiding heat which accompanies the emission of light by said light source; a light receiving element for receiving light reflected from said disk-shaped information recording medium; a sheet-shaped flexible circuit for feeding power to said light source and said light receiving element and communicating signals from said light receiving element; an optical bench for holding at least said light source, said radiator plate and said light receiving element; and a thermally conductive optical head cover fixed to said optical bench,
in which said radiator plate and the heat transfer member provided in said flexible circuit are brought into contact with each other, said flexible circuit is caused to guide heat from said radiator plate and, by bringing into contact the heat transfer member of said flexible circuit and said optical head cover with each other, heat generated by said light source is radiated through said light source through said optical head cover, said flexible circuit and said radiator plate,
characterized in that said optical head feed apparatus comprises a feed nut fixed to said optical head cover and having thermal conductivity; and a thermally conductive feed screw, fitted into said feed nut, for driving said optical head by rotating in the radial direction of said disk-shaped information recording medium, and
said optical head cover and said feed nut are either integrally configured or brought into contact with each other in a thermally conductive state thereby to transfer heat generated by said light source and transferred to said optical head cover to said feed screw through said feed nut and to radiate it.
Further, another aspect of the present invention is an optical head feed apparatus for feeding an optical head, said optical head having a light source for generating luminous energy required for recording on a disk-shaped information recording medium or reproducing information recorded on said disk-shaped information recording medium; a radiator plate, in contact with said light source either directly or indirectly, for guiding heat which accompanies the emission of light by said light source; an objective lens which is means for focusing light on said disk-shaped information recording medium; an objective lens drive unit for driving said objective lens in the focal and radial direction of said disk-shaped information recording medium; a light receiving element for receiving light reflected from said disk-shaped information recording medium; a sheet-shaped flexible circuit for feeding power and communicating signals to said light source and said light receiving element; a thermally conductive heat transfer member; an optical bench for holding at least said light source, said objective lens drive unit, said radiator plate, said light receiving element and said heat transfer member; and a thermally conductive optical head cover fixed to said optical bench,
said radiator plate and said heat transfer member are brought into contact with each other, said heat transfer member is caused to guide heat from said radiator plate and, by bringing into contact said heat transfer member and said optical head cover with each other, heat generated by said light source is radiated by said light source through said optical head cover, said heat transfer member and said radiator plate,
characterized in that said optical head feed apparatus comprises a feed nut fixed to said optical head cover and having thermal conductivity; and a thermally conductive feed screw, fitted into said feed nut, for driving said optical head by rotating in the radial direction of said disk-shaped information recording medium, and
said optical head cover and said feed nut are either integrally configured or brought into contact with each other in a thermally conductive state thereby to transfer heat generated by said light source and transferred to said optical head cover to said feed screw through said feed nut and to radiate it.
Further, another aspect of the present invention is an, optical head feed apparatus for feeding an optical head, said optical head having a light source for generating luminous energy required for recording on a disk-shaped information recording medium or reproducing information recorded on said disk-shaped information recording medium; a radiator plate, in contact with said light source either directly or indirectly, for guiding heat which accompanies the emission of light by said light source; an objective lens which is means for focusing light on said disk-shaped information recording medium; an objective lens drive unit for driving said objective lens in the focal and radial direction of said disk-shaped information recording medium; a light receiving element for receiving light reflected from said disk-shaped information recording medium; a sheet-shaped flexible circuit for feeding power and communicating signals to said light source and said light receiving element; a thermally conductive heat transfer member; and an optical bench for holding at least said light source, said objective lens drive unit, said radiator plate, said light receiving element and said heat transfer member,
characterized in that said optical head feed apparatus comprises a thermally conductive feed nut; and a thermally conductive feed screw, fitted into said feed nut, for driving said optical head by rotating in the radial direction of said disk-shaped information recording medium, and
said heat transfer member and said feed nut are either integrally configured or brought into contact with each other in a thermally conductive state thereby to transfer heat generated by said light source and transferred to said heat transfer member to said feed screw through said feed nut and to radiate it.